drivers/cpufreq/cpufreq_ondemand.c

   1 /*
   2  *  drivers/cpufreq/cpufreq_ondemand.c
   3  *
   4  *  Copyright (C)  2001 Russell King
   5  *            (C)  2003 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
   6  *                      Jun Nakajima <jun.nakajima@intel.com>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  */
  12
  13 #include <linux/kernel.h>
  14 #include <linux/module.h>
  15 #include <linux/smp.h>
  16 #include <linux/init.h>
  17 #include <linux/interrupt.h>
  18 #include <linux/ctype.h>
  19 #include <linux/cpufreq.h>
  20 #include <linux/sysctl.h>
  21 #include <linux/types.h>
  22 #include <linux/fs.h>
  23 #include <linux/sysfs.h>
  24 #include <linux/cpu.h>
  25 #include <linux/sched.h>
  26 #include <linux/kmod.h>
  27 #include <linux/workqueue.h>
  28 #include <linux/jiffies.h>
  29 #include <linux/kernel_stat.h>
  30 #include <linux/percpu.h>
  31 #include <linux/mutex.h>
  32
  33 /*
  34  * dbs is used in this file as a shortform for demandbased switching
  35  * It helps to keep variable names smaller, simpler
  36  */
  37
  38 #define DEF_FREQUENCY_UP_THRESHOLD              (80)
  39 #define MIN_FREQUENCY_UP_THRESHOLD              (11)
  40 #define MAX_FREQUENCY_UP_THRESHOLD              (100)
  41
  42 /*
  43  * The polling frequency of this governor depends on the capability of
  44  * the processor. Default polling frequency is 1000 times the transition
  45  * latency of the processor. The governor will work on any processor with
  46  * transition latency <= 10mS, using appropriate sampling
  47  * rate.
  48  * For CPUs with transition latency > 10mS (mostly drivers with CPUFREQ_ETERNAL)
  49  * this governor will not work.
  50  * All times here are in uS.
  51  */
  52 static unsigned int def_sampling_rate;
  53 #define MIN_SAMPLING_RATE_RATIO                 (2)
  54 /* for correct statistics, we need at least 10 ticks between each measure */
  55 #define MIN_STAT_SAMPLING_RATE                  (MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10))
  56 #define MIN_SAMPLING_RATE                       (def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
  57 #define MAX_SAMPLING_RATE                       (500 * def_sampling_rate)
  58 #define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER    (1000)
  59 #define TRANSITION_LATENCY_LIMIT                (10 * 1000)
  60
  61 static void do_dbs_timer(void *data);
  62
  63 struct cpu_dbs_info_s {
  64         cputime64_t prev_cpu_idle;
  65         cputime64_t prev_cpu_wall;
  66         struct cpufreq_policy *cur_policy;
  67         struct work_struct work;
  68         unsigned int enable;
  69 };
  70 static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
  71
  72 static unsigned int dbs_enable; /* number of CPUs using this policy */
  73
  74 /*
  75  * DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug
  76  * lock and dbs_mutex. cpu_hotplug lock should always be held before
  77  * dbs_mutex. If any function that can potentially take cpu_hotplug lock
  78  * (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then
  79  * cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock
  80  * is recursive for the same process. -Venki
  81  */
  82 static DEFINE_MUTEX (dbs_mutex);
  83 static DECLARE_WORK     (dbs_work, do_dbs_timer, NULL);
  84
  85 static struct workqueue_struct  *kondemand_wq;
  86
  87 struct dbs_tuners {
  88         unsigned int sampling_rate;
  89         unsigned int up_threshold;
  90         unsigned int ignore_nice;
  91 };
  92
  93 static struct dbs_tuners dbs_tuners_ins = {
  94         .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
  95         .ignore_nice = 0,
  96 };
  97
  98 static inline cputime64_t get_cpu_idle_time(unsigned int cpu)
  99 {
 100         cputime64_t retval;
 101
 102         retval = cputime64_add(kstat_cpu(cpu).cpustat.idle,
 103                         kstat_cpu(cpu).cpustat.iowait);
 104
 105         if (dbs_tuners_ins.ignore_nice)
 106                 retval = cputime64_add(retval, kstat_cpu(cpu).cpustat.nice);
 107
 108         return retval;
 109 }
 110
 111 /************************** sysfs interface ************************/
 112 static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
 113 {
 114         return sprintf (buf, "%u\n", MAX_SAMPLING_RATE);
 115 }
 116
 117 static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)
 118 {
 119         return sprintf (buf, "%u\n", MIN_SAMPLING_RATE);
 120 }
 121
 122 #define define_one_ro(_name)            \
 123 static struct freq_attr _name =         \
 124 __ATTR(_name, 0444, show_##_name, NULL)
 125
 126 define_one_ro(sampling_rate_max);
 127 define_one_ro(sampling_rate_min);
 128
 129 /* cpufreq_ondemand Governor Tunables */
 130 #define show_one(file_name, object)                                     \
 131 static ssize_t show_##file_name                                         \
 132 (struct cpufreq_policy *unused, char *buf)                              \
 133 {                                                                       \
 134         return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
 135 }
 136 show_one(sampling_rate, sampling_rate);
 137 show_one(up_threshold, up_threshold);
 138 show_one(ignore_nice_load, ignore_nice);
 139
 140 static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
 141                 const char *buf, size_t count)
 142 {
 143         unsigned int input;
 144         int ret;
 145         ret = sscanf (buf, "%u", &input);
 146
 147         mutex_lock(&dbs_mutex);
 148         if (ret != 1 || input > MAX_SAMPLING_RATE || input < MIN_SAMPLING_RATE) {
 149                 mutex_unlock(&dbs_mutex);
 150                 return -EINVAL;
 151         }
 152
 153         dbs_tuners_ins.sampling_rate = input;
 154         mutex_unlock(&dbs_mutex);
 155
 156         return count;
 157 }
 158
 159 static ssize_t store_up_threshold(struct cpufreq_policy *unused,
 160                 const char *buf, size_t count)
 161 {
 162         unsigned int input;
 163         int ret;
 164         ret = sscanf (buf, "%u", &input);
 165
 166         mutex_lock(&dbs_mutex);
 167         if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
 168                         input < MIN_FREQUENCY_UP_THRESHOLD) {
 169                 mutex_unlock(&dbs_mutex);
 170                 return -EINVAL;
 171         }
 172
 173         dbs_tuners_ins.up_threshold = input;
 174         mutex_unlock(&dbs_mutex);
 175
 176         return count;
 177 }
 178
 179 static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy,
 180                 const char *buf, size_t count)
 181 {
 182         unsigned int input;
 183         int ret;
 184
 185         unsigned int j;
 186
 187         ret = sscanf (buf, "%u", &input);
 188         if ( ret != 1 )
 189                 return -EINVAL;
 190
 191         if ( input > 1 )
 192                 input = 1;
 193
 194         mutex_lock(&dbs_mutex);
 195         if ( input == dbs_tuners_ins.ignore_nice ) { /* nothing to do */
 196                 mutex_unlock(&dbs_mutex);
 197                 return count;
 198         }
 199         dbs_tuners_ins.ignore_nice = input;
 200
 201         /* we need to re-evaluate prev_cpu_idle */
 202         for_each_online_cpu(j) {
 203                 struct cpu_dbs_info_s *dbs_info;
 204                 dbs_info = &per_cpu(cpu_dbs_info, j);
 205                 dbs_info->prev_cpu_idle = get_cpu_idle_time(j);
 206                 dbs_info->prev_cpu_wall = get_jiffies_64();
 207         }
 208         mutex_unlock(&dbs_mutex);
 209
 210         return count;
 211 }
 212
 213 #define define_one_rw(_name) \
 214 static struct freq_attr _name = \
 215 __ATTR(_name, 0644, show_##_name, store_##_name)
 216
 217 define_one_rw(sampling_rate);
 218 define_one_rw(up_threshold);
 219 define_one_rw(ignore_nice_load);
 220
 221 static struct attribute * dbs_attributes[] = {
 222         &sampling_rate_max.attr,
 223         &sampling_rate_min.attr,
 224         &sampling_rate.attr,
 225         &up_threshold.attr,
 226         &ignore_nice_load.attr,
 227         NULL
 228 };
 229
 230 static struct attribute_group dbs_attr_group = {
 231         .attrs = dbs_attributes,
 232         .name = "ondemand",
 233 };
 234
 235 /************************** sysfs end ************************/
 236
 237 static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
 238 {
 239         unsigned int idle_ticks, total_ticks;
 240         unsigned int load;
 241         cputime64_t cur_jiffies;
 242
 243         struct cpufreq_policy *policy;
 244         unsigned int j;
 245
 246         if (!this_dbs_info->enable)
 247                 return;
 248
 249         policy = this_dbs_info->cur_policy;
 250         cur_jiffies = jiffies64_to_cputime64(get_jiffies_64());
 251         total_ticks = (unsigned int) cputime64_sub(cur_jiffies,
 252                         this_dbs_info->prev_cpu_wall);
 253         this_dbs_info->prev_cpu_wall = cur_jiffies;
 254         /*
 255          * Every sampling_rate, we check, if current idle time is less
 256          * than 20% (default), then we try to increase frequency
 257          * Every sampling_rate, we look for a the lowest
 258          * frequency which can sustain the load while keeping idle time over
 259          * 30%. If such a frequency exist, we try to decrease to this frequency.
 260          *
 261          * Any frequency increase takes it to the maximum frequency.
 262          * Frequency reduction happens at minimum steps of
 263          * 5% (default) of current frequency
 264          */
 265
 266         /* Get Idle Time */
 267         idle_ticks = UINT_MAX;
 268         for_each_cpu_mask(j, policy->cpus) {
 269                 cputime64_t total_idle_ticks;
 270                 unsigned int tmp_idle_ticks;
 271                 struct cpu_dbs_info_s *j_dbs_info;
 272
 273                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 274                 total_idle_ticks = get_cpu_idle_time(j);
 275                 tmp_idle_ticks = (unsigned int) cputime64_sub(total_idle_ticks,
 276                                 j_dbs_info->prev_cpu_idle);
 277                 j_dbs_info->prev_cpu_idle = total_idle_ticks;
 278
 279                 if (tmp_idle_ticks < idle_ticks)
 280                         idle_ticks = tmp_idle_ticks;
 281         }
 282         load = (100 * (total_ticks - idle_ticks)) / total_ticks;
 283
 284         /* Check for frequency increase */
 285         if (load > dbs_tuners_ins.up_threshold) {
 286                 /* if we are already at full speed then break out early */
 287                 if (policy->cur == policy->max)
 288                         return;
 289
 290                 __cpufreq_driver_target(policy, policy->max,
 291                         CPUFREQ_RELATION_H);
 292                 return;
 293         }
 294
 295         /* Check for frequency decrease */
 296         /* if we cannot reduce the frequency anymore, break out early */
 297         if (policy->cur == policy->min)
 298                 return;
 299
 300         /*
 301          * The optimal frequency is the frequency that is the lowest that
 302          * can support the current CPU usage without triggering the up
 303          * policy. To be safe, we focus 10 points under the threshold.
 304          */
 305         if (load < (dbs_tuners_ins.up_threshold - 10)) {
 306                 unsigned int freq_next;
 307                 freq_next = (policy->cur * load) /
 308                         (dbs_tuners_ins.up_threshold - 10);
 309
 310                 __cpufreq_driver_target(policy, freq_next, CPUFREQ_RELATION_L);
 311         }
 312 }
 313
 314 static void do_dbs_timer(void *data)
 315 {
 316         unsigned int cpu = smp_processor_id();
 317         struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, cpu);
 318
 319         dbs_check_cpu(dbs_info);
 320         queue_delayed_work_on(cpu, kondemand_wq, &dbs_info->work,
 321                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 322 }
 323
 324 static inline void dbs_timer_init(unsigned int cpu)
 325 {
 326         struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, cpu);
 327
 328         INIT_WORK(&dbs_info->work, do_dbs_timer, 0);
 329         queue_delayed_work_on(cpu, kondemand_wq, &dbs_info->work,
 330                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 331         return;
 332 }
 333
 334 static inline void dbs_timer_exit(unsigned int cpu)
 335 {
 336         struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, cpu);
 337
 338         cancel_rearming_delayed_workqueue(kondemand_wq, &dbs_info->work);
 339 }
 340
 341 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 342                                    unsigned int event)
 343 {
 344         unsigned int cpu = policy->cpu;
 345         struct cpu_dbs_info_s *this_dbs_info;
 346         unsigned int j;
 347
 348         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 349
 350         switch (event) {
 351         case CPUFREQ_GOV_START:
 352                 if ((!cpu_online(cpu)) ||
 353                     (!policy->cur))
 354                         return -EINVAL;
 355
 356                 if (policy->cpuinfo.transition_latency >
 357                                 (TRANSITION_LATENCY_LIMIT * 1000)) {
 358                         printk(KERN_WARNING "ondemand governor failed to load "
 359                                "due to too long transition latency\n");
 360                         return -EINVAL;
 361                 }
 362                 if (this_dbs_info->enable) /* Already enabled */
 363                         break;
 364
 365                 mutex_lock(&dbs_mutex);
 366                 dbs_enable++;
 367                 if (dbs_enable == 1) {
 368                         kondemand_wq = create_workqueue("kondemand");
 369                         if (!kondemand_wq) {
 370                                 printk(KERN_ERR "Creation of kondemand failed\n");
 371                                 dbs_enable--;
 372                                 mutex_unlock(&dbs_mutex);
 373                                 return -ENOSPC;
 374                         }
 375                 }
 376                 for_each_cpu_mask(j, policy->cpus) {
 377                         struct cpu_dbs_info_s *j_dbs_info;
 378                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
 379                         j_dbs_info->cur_policy = policy;
 380
 381                         j_dbs_info->prev_cpu_idle = get_cpu_idle_time(j);
 382                         j_dbs_info->prev_cpu_wall = get_jiffies_64();
 383                 }
 384                 this_dbs_info->enable = 1;
 385                 sysfs_create_group(&policy->kobj, &dbs_attr_group);
 386                 /*
 387                  * Start the timerschedule work, when this governor
 388                  * is used for first time
 389                  */
 390                 if (dbs_enable == 1) {
 391                         unsigned int latency;
 392                         /* policy latency is in nS. Convert it to uS first */
 393                         latency = policy->cpuinfo.transition_latency / 1000;
 394                         if (latency == 0)
 395                                 latency = 1;
 396
 397                         def_sampling_rate = latency *
 398                                         DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
 399
 400                         if (def_sampling_rate < MIN_STAT_SAMPLING_RATE)
 401                                 def_sampling_rate = MIN_STAT_SAMPLING_RATE;
 402
 403                         dbs_tuners_ins.sampling_rate = def_sampling_rate;
 404                 }
 405                 dbs_timer_init(policy->cpu);
 406
 407                 mutex_unlock(&dbs_mutex);
 408                 break;
 409
 410         case CPUFREQ_GOV_STOP:
 411                 mutex_lock(&dbs_mutex);
 412                 dbs_timer_exit(policy->cpu);
 413                 this_dbs_info->enable = 0;
 414                 sysfs_remove_group(&policy->kobj, &dbs_attr_group);
 415                 dbs_enable--;
 416                 if (dbs_enable == 0)
 417                         destroy_workqueue(kondemand_wq);
 418
 419                 mutex_unlock(&dbs_mutex);
 420
 421                 break;
 422
 423         case CPUFREQ_GOV_LIMITS:
 424                 lock_cpu_hotplug();
 425                 mutex_lock(&dbs_mutex);
 426                 if (policy->max < this_dbs_info->cur_policy->cur)
 427                         __cpufreq_driver_target(
 428                                         this_dbs_info->cur_policy,
 429                                         policy->max, CPUFREQ_RELATION_H);
 430                 else if (policy->min > this_dbs_info->cur_policy->cur)
 431                         __cpufreq_driver_target(
 432                                         this_dbs_info->cur_policy,
 433                                         policy->min, CPUFREQ_RELATION_L);
 434                 mutex_unlock(&dbs_mutex);
 435                 unlock_cpu_hotplug();
 436                 break;
 437         }
 438         return 0;
 439 }
 440
 441 static struct cpufreq_governor cpufreq_gov_dbs = {
 442         .name           = "ondemand",
 443         .governor       = cpufreq_governor_dbs,
 444         .owner          = THIS_MODULE,
 445 };
 446
 447 static int __init cpufreq_gov_dbs_init(void)
 448 {
 449         return cpufreq_register_governor(&cpufreq_gov_dbs);
 450 }
 451
 452 static void __exit cpufreq_gov_dbs_exit(void)
 453 {
 454         cpufreq_unregister_governor(&cpufreq_gov_dbs);
 455 }
 456
 457
 458 MODULE_AUTHOR ("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
 459 MODULE_DESCRIPTION ("'cpufreq_ondemand' - A dynamic cpufreq governor for "
 460                 "Low Latency Frequency Transition capable processors");
 461 MODULE_LICENSE ("GPL");
 462
 463 module_init(cpufreq_gov_dbs_init);
 464 module_exit(cpufreq_gov_dbs_exit);